Pregnant women: Just don't drink, study suggests

After years of confusing and contradictory advice about alcohol consumption during pregnancy, a new study may have the final word: Just don’t drink. The study, published Wednesday in the journal PLoS ONE, reveals that even a few drinks a week by an expectant mother can lead to reductions in a child’s IQ if the child has certain genetic variations impairing their ability to break down alcohol.

Research into the effects of alcohol consumption during pregnancy has generally focused on heavy drinking, and the resulting incidence of fetal alcohol syndrome. Meanwhile, observational studies of moderate drinking have shown little negative effect. As a result, many physicians advise their expectant patients that a drink every now and then is fine, so long as the drinking never becomes heavy.

The new report specifically looked at mothers who consumed between one and six drinks a week. As an added layer, the researchers also analyzed the DNA of the children to look for differences in the parts of the genetic code responsible for breaking down alcohol — an important consideration that can drastically change the effect of a drink on the body.

By using a biological variable to ask whether small doses of alcohol have the potential to cause harm, the researchers eliminated concerns about sociological or socioeconomic differences between abstainers and drinkers.

The study identified four unique genetic variations in the ADH gene -- which produces an enzyme responsible for breaking down alcohol -- that had a harmful effect on a child’s IQ: For each variation a child had, their IQ was roughly two points lower.

The effect was seen only among mothers who drank, and was present even when mothers drank very little (the study excluded mothers who drank heavily).

The results suggest that children with an impaired ability to break down alcohol can be harmed by relatively small amounts of it while in the womb.

On the one hand, the results show that children who lack the genetic variants uncovered in the study may not suffer from their mother’s moderate drinking.

But the study also underscores why one might want to use the precautionary principle during pregnancy: In the right situation, even an occasional glass of wine appears to carry with it the risk of a drop in IQ.